The colonial cyanobacterium Microcystis proliferates in a wide range of freshwater ecosystems and is exposed to changing environmental factors during its life cycle. Microcystis blooms are often ...toxic, potentially fatal to animals and humans, and may cause environmental problems. There has been little investigation of the genomics of these cyanobacteria.
Deciphering the 5,172,804 bp sequence of Microcystis aeruginosa PCC 7806 has revealed the high plasticity of its genome: 11.7% DNA repeats containing more than 1,000 bases, 6.8% putative transposases and 21 putative restriction enzymes. Compared to the genomes of other cyanobacterial lineages, strain PCC 7806 contains a large number of atypical genes that may have been acquired by lateral transfers. Metabolic pathways, such as fermentation and a methionine salvage pathway, have been identified, as have genes for programmed cell death that may be related to the rapid disappearance of Microcystis blooms in nature. Analysis of the PCC 7806 genome also reveals striking novel biosynthetic features that might help to elucidate the ecological impact of secondary metabolites and lead to the discovery of novel metabolites for new biotechnological applications. M. aeruginosa and other large cyanobacterial genomes exhibit a rapid loss of synteny in contrast to other microbial genomes.
Microcystis aeruginosa PCC 7806 appears to have adopted an evolutionary strategy relying on unusual genome plasticity to adapt to eutrophic freshwater ecosystems, a property shared by another strain of M. aeruginosa (NIES-843). Comparisons of the genomes of PCC 7806 and other cyanobacterial strains indicate that a similar strategy may have also been used by the marine strain Crocosphaera watsonii WH8501 to adapt to other ecological niches, such as oligotrophic open oceans.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Whole‐genome comparisons of the tubercle bacilli were undertaken using ordered bacterial artificial chromosome (BAC) libraries of Mycobacterium tuberculosis and the vaccine strain, Mycobacterium ...bovis BCG‐Pasteur, together with the complete genome sequence of M. tuberculosis H37Rv. Restriction‐digested BAC arrays of M. tuberculosis H37Rv were used in hybridization experiments with radiolabelled M. bovis BCG genomic DNA to reveal the presence of 10 deletions (RD1–RD10) relative to M. tuberculosis. Seven of these regions, RD4–RD10, were also found to be deleted from M. bovis, with the three M. bovis BCG‐specific deletions being identical to the RD1–RD3 loci described previously. The distribution of RD4–RD10 in Mycobacterium africanum resembles that of M. tuberculosis more closely than that of M. bovis, whereas an intermediate arrangement was found in Mycobacterium microti, suggesting that the corresponding genes may affect host range and virulence of the various tubercle bacilli. Among the known products encoded by these loci are a copy of the proposed mycobacterial invasin Mce, three phospholipases, several PE, PPE and ESAT‐6 proteins, epoxide hydrolase and an insertion sequence. In a complementary approach, direct comparison of BACs uncovered a third class of deletions consisting of two M. tuberculosis H37Rv loci, RvD1 and RvD2, deleted from the genome relative to M. bovis BCG and M. bovis. These deletions affect a further seven genes, including a fourth phospholipase, plcD. In summary, the insertions and deletions described here have important implications for our understanding of the evolution of the tubercle complex.
Billault Alain. Lucien, l’âne et la métamorphose dans Lucius ou l’âne. In: Revue des Études Grecques, tome 132, fascicule 1, Janvier-juin 2019. pp. 263-275.
The author of On the Sublime uses poetry as a fount of illustrations and arguments for his discussions of rhetoric, but also as a well-spring of beauty from which he derives aesthetical judgments and ...theories. This use of poetry reveals its situation as a bulk of textual data available for any intellectual project and as living literature. It also enables us to catch a sight of the two faces of Longinus, a theoretician of rhetoric and a literary critic.
L’auteur de traité Du sublime utilise la poésie comme un gisement d’illustrations et de preuves pour ses démonstrations relatives à la rhétorique, mais aussi comme une source de beauté qui lui inspire des jugements et des théories esthétiques. Cette utilisation de la poésie révèle sa situation comme ensemble de données textuelles disponibles pour tout projet intellectuel et comme littérature vivante. Elle nous permet aussi d’apercevoir le double visage de Longin, théoricien de la rhétorique et critique littéraire.
Mixis Marquis, Émeline; Billault, Alain
2017
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Observateur hors pair, critique acerbe, orateur virtuose qui manie l’humour et l’ironie tout autant qu’il se plaît aux références intertextuelles et aux réflexions métalittéraires, Lucien de Samosate ...est un des grands noms du IIe siècle après J.-C. Son influence sur des œuvres aussi variées que l’Éloge de la Folie d’Érasme, Pantagruel et Gargantua de Rabelais, les Dialogues des morts de Fontenelle, les Voyages de Gulliver de Swift et les Petites œuvres morales de Leopardi témoigne de l’étendue de ses expérimentations littéraires.C’est à l’une des spécificités de l’écriture lucianesque, la mixis, que le présent ouvrage est consacré. Le mélange des genres à l’œuvre chez Lucien y est examiné par un ensemble de spécialistes dans ses dimensions théoriques et pratiques. En effet, si Lucien se revendique fièrement comme l’inventeur d’un type particulier de mélange, le dialogue comique, une multiplicité d’autres formes, d’autres « ingrédients » sont convoqués dans ses textes. En s’interrogeant sur la nature de la mixis, sur ses modalités et sur ses fonctions, ainsi que sur ses effets, il s’agit de proposer une synthèse sur un des éléments clés de la poétique lucianesque
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